The present invention relates to a semiconductor device; and, more particularly, to a method for manufacturing a gate structure incorporated therein aluminum oxide (Al2O3) as a gate dielectric.
As is well known, a semiconductor device has been down-sized by a scale down of a design rule. Therefore, a gate oxide tends to rapidly approach 30 xc3x85 in thickness and below to increase the capacitance between a gate electrode and a channel region. However, the use of silicon dioxide as a gate dielectric is limited at this thickness and below. Once silicon dioxide (SiO2) is formed to a thickness of less than 30 xc3x85, direct tunneling may occur through the gate dielectric to the channel region, thereby increasing a leakage current associated with the gate electrode and the channel region, causing an increase in power consumption.
Since reducing the thickness of the gate dielectric inherently increases the gate-to-channel leakage current, alternative methods have been developed to reduce this leakage current while maintaining thin SiO2 equivalent thickness. One of these methods is to use a high K dielectric material such as tantalum oxide (Ta2O5) as the gate dielectric materials to increase the capacitance between the gate and the channel.
However, if a poly-silicon is utilized as a gate electrode, the use of Ta2O5 for gate dielectric materials has a disadvantage in integrating the semiconductor device. That is, an undesired SiO2 is formed at an interface between Ta2O5 and the poly-silicon, which, in turn, increases an equivalent oxide thickness. In order to overcome this problem, a barrier metal such as titanium nitride (TiN) is employed. However, the TiN makes a threshold voltage shift changed.
Therefore, there is still a demand for developing a high K dielectric as a gate oxide with excellent leakage current as well as a low interface state with both a gate electrode and a silicon substrate.
It is, therefore, an object of the present invention to provide a method for manufacturing a gate structure incorporated therein aluminum oxide as a gate oxide for use in a semiconductor device.
In accordance with one aspect of the present invention, there is provided a method for manufacturing a gate structure for use in a semiconductor device, the method comprising the steps of: a) preparing a semiconductor substrate provided with an isolation region formed therein; b) forming an aluminum oxide layer (Al2O3) on the semiconductor substrate; c) carrying out a Si+ plasma doping on the Al2O3 layer; d) annealing the Al2O3 layer doped with the silicon ions; e) forming a conductive layer on top of the Al2O3 layer; and f) patterning the conductive layer, thereby obtaining the gate structure.